Читать книгу Are the Effects of Use and Disuse Inherited? - Ball William Platt - Страница 4

The next example, the reduced biting muscles, &c., of lap-dogs is also unsatisfactory as a proof of the inheritance of the effects of disuse; for the change can readily be accounted for without the introduction of such a factor. The previous natural selection of strong jaws and teeth and muscles is reversed. The conscious or unconscious selection of lap-dogs with the least tendency to bite would easily bring about a general enfeeblement of the whole biting apparatus – weakness of the parts concerned favouring harmlessness. Mr. Spencer maintains that the dwindling of the parts concerned in clenching the jaw is certainly not due to artificial selection because the modifications offer no appreciable external signs. Surely hard biting is sufficiently appreciable by the person bitten without any visual admeasurement of the masseter muscles or the zygomatic arches. Disuse during lifetime would also cause some amount of degeneracy; and I am not sure that Mr. Spencer is right in entirely excluding economy of nutrition from the problem. Breeders would not over-feed these dogs; and the puppies that grew most rapidly would usually be favoured.